1. Field of the Invention
The present invention relates to an image storage/retrieval apparatus for retrieving a desired image by designating one of a plurality of keywords which are assigned to respective images, thereby obtaining high-speed retrieval process. It is related more particularly to an image storage/retrieval apparatus wherein a plurality of keywords are classified into several groups. Specifically a group corresponding to respective keywords is assigned to images when the images are stored, a bit at a position corresponding to a given group is enabled and the remaining bits are disabled to calculate a value, this value is called an image group keyword. A pair of the image group keywords and their corresponding images are then stored. When a retrieval group keyword, in which the bit corresponding to the given image group is enabled, is calculated from a keyword input, an image group keyword is compared with the retrieval group keyword. Candidate images to be retrieved are determined and extracted in units of a plurality of keywords, and conventional retrieval which is performed using keywords as units is performed on the extracted candidate images to extract a desired image from the candidate images.
2. Description of the Related Art
In recent years, an image storage/retrieval apparatus such as an image filing apparatus has been used in practice. In the image storage/retrieval apparatus, images such, as a large number of documents, are optically read by a two-dimensional scanner in the two-dimensional scanning process, the read images are stored in an optical disk, and the arbitrary image stored in the optical disk is retrieved, read out, and output in a visual state at an output unit such as a CRT display unit or a printer.
In the above apparatus, a method such as a free text retrieving method is utilized. That is, in order to find a target image, a retrieval keyword is input, keyword retrieval for selecting an image assigned with the keyword is performed, a character string for retrieval is input, and the image assigned with a title including the character string is selected.
In the above image filing apparatus, a keyword and a title assigned to each managed image are both stored in an optical disk at a storage destination used for storing images, and in a magnetic disk serving as another hardware. When the above retrieving process is to be performed, keywords and titles assigned to all managed images are read out from the optical disk or the magnetic disk, and the keywords and the titles are compared with an input retrieval keyword and an input character string.
In general, keyword numbers are assigned to keywords assigned to images, and the keyword numbers are recorded in units of images.
In such a system, assume that the number of managed images is 1,000, that the average number of keywords assigned to each image is 5, and that a keyword number is expressed by 2 bytes. In this case, data of 10 bytes is read out per image, i.e., data of 10,000 bytes (about 10 kB) is read out as a whole, and the data is compared with a retrieval keyword.
When a character string length of a title assigned to an image is 100 bytes, a total of data of 100,000 bytes (about 100 kB) is read out and compared with a retrieval character string.
Therefore, when the number of managed images or the number of keywords assigned to the images is increased or when the character string length of titles assigned to the images is increased, the amount of data to be compared with a retrieval keyword or a retrieval character string is largely increased, thereby requiring increased retrieval time.